Cathode ray tube having an annular-shaped rear window

ABSTRACT

A rear-window cathode ray tube having a longitudinal axis and an envelope of substantially glass construction wherein there is oriented a cathodoluminescent screen and at least one related electron gun. The envelope has a substantially annular-shaped optical access window therein oriented in substantially symmetrical relationship to the longitudinal axis of the tube to provide a substantially annular viewing area for observing the electron impinged side of the screen.

United States Patent lnventor Alfred D. Johnson Seneca Falls, N.Y. 785,646

Dec. 20, 1968 May 25, 1971 Appl. No. Filed Patented Assignee Sylvania Electric Products lnc.

CATHODE RAY TUBE HAVING AN ANNULAR- SHAPED REAR WINDOW 1 Claim, 2 Drawing Figs.

US. Cl.

Field of Search References Cited UNITED STATES PATENTS Primary Examiner-Roy Lake Assistant Examiner--Palmer C. Demeo Attorneys-Cyril A. Krenzer and Frederick H. Rinn ABSTRACT: A rear-window cathode ray tube having a longitudinal axis and an envelope of substantially glass construction wherein there is oriented a cathodoluminescent screen and at least one related electron gun. The envelope has a substantially annular-shaped optical access window therein oriented in substantially symmetrical relationship to the longitudinal axis of the tube to provide a substantially annular 2,398,960 4/1946 Prosser 313/91X viewing area for observing the electron impinged side of the 2,432,908 12/1947 Leverenz 313/91 screen.

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INVENTOR. ALFRED D. JOHNSON Qua.

ATTORNEY CATHODIE RAY TUBE HAVING AN ANNULAR-SI'IAPED REAR WINDOW BACKGROUND OF THE INVENTION The invention relates to cathode ray tubes and more particularly to an improved rear-window type of cathode ray tube and the associated envelope structure for a tube of that type. In certain information display systems, rear-window cathode ray tubes are employed to facilitate full presentation and observation of the display. Such tubes not only provide the conventional frontal viewing area but also have one or more portal provisions oriented in the funnel portion of the tube envelope to permit viewing of the rear surface of the screen. Through this type of funnel oriented viewing port, it is possible to observe, photograph, or project a superimposed image on the information displayed on the screen without interfering with the frontal observation thereof. Since a large number of the conventional rear-window tubes are limited to one or two observation ports, a decision must be made whether to observe, record or project information through a respective port or ports as all media cannot be utilized simultaneously at one or two openings. Furthermore, exact positioning of the projection and photographic equipment is determined by the orientation of the respective viewing port or ports. The incorporation of a plurality of optical ports into the funnel portion of the envelope becomes a critically exacting and expensive glass working operation.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned difficulties and to provide an improved rear-window type of cathode ray tube having an extensive provision for rear view utilization.

Another object is to provide an improved rear-window type of cathode ray tube which permits rear view utilization from a number of angles.

The foregoing objects are achieved in one aspect of the invention by the provision of an improved rear-window cathode ray tube having an envelope wherein the funnel or bulb portion is perimetrically mated and sealed to a substantially transparent annular plate of optical quality. A tubular neck section is sealed to the substantially centrally oriented aperture in the annular plate. The sealing of the bulb and neck portions to the annular plate is done in a manner to prevent optical distortion of the plate. Thus, there is provided an annular rear-window tube which permits simultaneous back-of-the-screen projection, photographing and observation of the information displayed on the cathodoluminescent screen of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the rear-window cathode ray tube of the invention; and

FIG. 2 is a plan view taken along the line 2-2 of FIG. 1 illustrating the expansive area of the annular rear window portal showing an electrical conductive means thereacross.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

With reference to FIG. 1 there is shown a rear-window cathode ray tube 11 having a face panel portion 13 upon which is interiorly disposed a cathodoluminescent screen 15. Integral with the face panel portion is the funnel or bulb portion 17 to which is sealed a substantially transparent annular plate 19 of optical quality. A tubular neck section 21 is sealed to the centrally oriented aperture 23 of the annular plate to complete the envelope structure. At least one electron source 25 is mounted in the tubular neck in a manner to beam electrons to the screen to form a cathodoluminescent image therein. The light transmissive plate 19 forms an annularshaped optical window which provides extensive visual access to the rear of the screen.

As one embodiment, a round tube is shown and described such as, for example, one having an external envelope diameter within the range of 5 to 6 inches. It is not intended that the size or shape be limiting. In addition, the term annular" as used herein is intended to include any shape of substantially continuous optical viewing window oriented to surround the axial oriented tubular neck portion ofthe tube.

In greater detail, the tube 11 has a longitudinal axis 12 extending therethrough from the face to the base portions thereof. The componental parts of the envelope structure have compatible thermal expansion coefficients to insure her metic jointures therebetween.

The substantially planar face panel portion 13 is of a nonbrowning-type glass having a defined perimetric shape to facilitate a hermetic seal with the compatibly formed first end 27 of the bulb portion 17. The interior surface of the face panel, upon which the screen is formed, is uniformly abraded to provide a fine diffusive surface on the glass to reduce the hotspot effect resultant from light projected imagery focused on the rear of the screen.

A cathodoluminescent screen 15 is suitably disposed on the abraded interior surface of the face plate 13 by conventional means, as, for example, by the settling technique. The phosphor materials employed are chosen to best suit the conditions under which the tube is to be utilized. Usually the phosphor is of a fine particle size having medium persistence and of an excited hue and brightness to advantageously present the desired informational display.

A substantially transparent annular plate 19, such as G-l2 optical quality glass, is formed to have outer and inner peripheries or boundaries 29 and 31 respectively. These define an annular region 33 therebetween which constitutes an annular shaped planar viewing window that is spacedly re lated in a substantially symmetrical manner about the longitudinal axis of the tube. The inner periphery 31 defines a substantially centrally oriented opening or aperture 23, while the outer periphery 29 of the annular plate is formed to substantially perimetrically match the second end 35 of the bulb portion. The bulb is placed on the plate and is hermetically sealed thereto in a manner to maintain the optical quality of the viewing window 33. Specifically, the heremetic jointure between the bulb portion 17 and the annular plate 19 is consummated by utilizing a sandwich-type filling therebetween in the form of a continuous band of glass solder or frit. 37 which has a melting temperature much lower than the softening temperatures of the respective glass portions joined together.

A substantially tubular neck section 21 of the tube has first and second ends, 41 and 43 respectively; of which the first end 41 is formed to substantially match and seat in the centrally oriented aperture 23 in the annular plate. A heremetic seal is made between the seated neck and plate portions by disposing a continuous band therebetween of glass frit 37' similar to that utilized in making the aforementioned bulb-to-plate seal. A bead of frit 39 is applied exteriorly to both strengthen and hermetically insure the neck-to-plate seal. Thus, the perimetrically oriented hermetic seals of the annular plate are accomplished at temperatures that are not detrimental to the optical properties of the annular window member. It is to be noted that the annular optical plate provides a structural foundation for the envelope. It exhibits a sufficient thickness x" to be free of optical distortion while accommodating the respective 'weight factors of the associated bulb and neck portions.

One or moreelectron gun(s) is/are positioned within the neck section of the tube in a manner to beam electrons to the screen. As shown, an undetailed source of electrons 25 denotes the presence of one or several guns. In this instance, both focusing and deflection are accomplished by electrostatic means which eliminates the need. for externally oriented yoke means.

A stem portion 45, which supports the sourceof electrons 25, is hermetically sealed to the terminal or second end 43 of the neck section by a conventional sealing technique. Electrical connective means 47 extend from the stem through the base 49 to provide external connections for the tube.

The interior surface of the bulb portion 17 has two separated bands of conductive material, such as aquadag, ap-

plied thereto. The first of these bands 51 is oriented adjacent the screen area and makes electrical contact with the high voltage anode button 53 located in the bulb or funnel portion 17. The second conductive band 55, of similar material, is disposed on the bulb wall near the optical window 33. Electrically joining the two bands is a conventional accelerating spiral 57 of resistive material.

A neck conductive band 59 is applied to the upper part of the tubular neck section 21. Electrical connection between this neck-disposed band and the electron source 25 is effected by connective means 61, such as the conventional resilient contactors usually affixed to the electron gun.

Operation of the tube is dependent upon an electrical connection between the neck conductive band 59 and the second conductive band 55 on the bulb. This is expeditiously effected by applying a conductive path 63 to the inner bulb surface to extend from the second band thereon to the annular optical plate 19, whereupon at least one radial conductive stripe 65, such as of aquadag or tin oxide coating, is applied to the surface 34 to complete an electrical path between the neck and bulb conductive coatings.

In operation, the electron gun 25 of the rear-window tube 11 receives the display signal information through the electrical connective means 47 in conjunction with the final anode voltage applied to the high voltage button 53 on the bulb portion 17. The electron beam emanating from the electron gun is electrostatically focused and deflected to appropriately scan the cathodoluminescent screen through the predetermined angle of deflection 0. The electron excited phosphors in the screen provide a luminescent display of information which is readily observed from either side of the screen, i.e. through the face plate 13 or the annular rear-window 33.

Expansive rear-view utilization in excess of 300 is provided by this tube. For example, in addition to visual observation, photographic means 67 having optics of a predetermined angle of width 6, can be oriented to focus on the screen image through the annular window 33. Likewise, simultaneously, projection means 69 can be oriented in a similar manner to project a superimposed image on the screen display, for example a grid or map overlay. Since the interior surface of the face panel is uniformly and finely abraded there is a noticeable reduction of the hot spot effect of the image projected on the rear of the screen. Thus, the annular window adequately and simultaneously accommodates a variety of related utilizations such as photographing the screen display and projecting auxiliary imagery thereon in addition to visual observation of the dynamic display. The extensive expanse of viewing area afforded by the annular-shaped rear-window affords viewing utilization from a number of angles. Such versatile and simultaneous utility is not possible with the conventional single or dual port rear-view tubes known in the art.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

lclaim: 1. In a rear-window cathode ray tube having a longitudinal axis comprising:

a cathodoluminescent screen; at least one electron source positioned in said tube relative to said screen to beam electrons thereto; and a glass envelope including face panel, bulb, and neck portions formed to provide an enclosure for said screen and said electron source, said face panel portion h avin a defined penmetnc shape; said bulb portion having rrst and second ends, said first end being compatibly formed to perimetrically mate with said face panel portion to which it is hermetically sealed; said envelope having a substantially planar transparent annular plate of optical quality glass associated with the second end of said bulb portion and formed to have both outer and inner peripheries with the annular region defined therebetween constituting an annular shaped viewing port spacedly related in a substantially perpendicular and symmetrical manner about said longitudinal axis, said annular plate being of a thickness greater than that of said bulb and neck sections to provide structural foundation for said tube envelope and being free of optical distortion while accommodating the respective weight factors of the associated bulb and neck portions, said outer periphery of said annular viewing area being substantially matched with the perimeter of said second end of said bulb portion and hermetically sealed therewith by a material having a melting temperature lower than the softening temperatures of the respective glass portions joined to maintain the optical quality of said viewing window, said inner periphery defining a substantially centrally oriented aperture; said neck section being substantially tubular and having first and second ends, said first end being substantially matched to seat in the centrally oriented aperture in said annular plate and hermetically sealed therewith by a sealing material having a melting temperature lower than the softening temperatures of the respective glass portions joined to maintain the optical quality of said annular viewing window, said second end being formed to match a related stem portion associated and joined therewith.

UNITED STATES PATENT OFFICE 3,581,134 May 25, 1971 Y Patent 'No. Dated Invsntofl s) ALFRED D. JOHNSON It is certified that error appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

In Column 1 of the Patent, CROSS-REFERENCE TO RELATED APPLICATIONS has been omitted. Please insert CROSS-REFERENCES TO RELATED APPLICATIONS This application contains matter disclosed but not claimed in two related United States patent applications filed concurrently herewith and assigned to the assignee of the present invention. These applications are: S.N. 785,647 "Method and Apparatus for Fabricating a Cathode Ray Tube Having an Annular Shaped Rear Window", and S.N. 785,648 "Means for Controlling Electrostatic Charge on the Rear Window of a Cathode Ray Tube.

Signed and sealed this 114th day of December 1971;.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

1. In a rear-window cathode ray tube having a longitudinal axis comprising: a cathodoluminescent screen; at least one electron source positioned in said tube relative to said screen to beam electrons thereto; and a glass envelope including face panel, bulb, and neck portions formed to provide an enclosure for said screen and said electron source, said face panel portion having a defined perimetric shape; said bulb portion having first and second ends, said first end being compatibly formed to perimetrically mate with said face panel portion to which it is hermetically sealed; said envelope having a substantially planar transparent annular plate of optical quality glass associated with the second end of said bulb portion and formed to have both outer and inner peripheries with the annular region defined therebetween constituting an annular shaped viewing port spacedly related in a substantially perpendicular and symmetrical manner about said longitudinal axis, said annular plate being of a thickness greater than that of said bulb and neck sections to provide structural foundation for said tube envelope and being free of optical distortion while accommodating the respective weight factors of the associated bulb and neck portions, said outer periphery of said annular viewing area being substantially matched with the perimeter of said second end of said bulb portion and hermetically sealed therewith by a material having a melting temperature lower than the softening temperatures of the respective glass portions joined to maintain the optical quality of said viewing window, said inner periphery defining a substantially centrally oriented aperture; said neck section being substantially tubular and having first and second ends, said first end being substantially matched to seat in the centrally oriented aperture in said annular plate and hermetically sealed therewith by a sealing material having a melting temperature lower than the softening temperatures of the respective glass portions joined to maintain the optical quality of said annular viewing window, said second end being formed to match a related stem portion associated and joined therewith. 